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International audience; Graphene (Gr) is known to be an excellent barrier preventing atoms and molecules to diffuse through it. This is due to the carbon atom arrangement in a two-dimensional (2D) honeycomb structure with a very small lattice parameter thus forming an electron cloud that prevents atoms and molecules crossing. Nonetheless at high an-nealing temperatures, intercalation of atoms through graphene occurs, opening the path for formation of vertical heterojunctions constituted of two-dimensional layers. In this paper, we report on the ability of silicon atoms to penetrate the graphene network, fully epitaxially grown on a Ni(111) surface, even at room temperature. Our scanning tunneling microscopy (STM) experiments show that the presence of defects like vacancies and disloca-tions in the graphene lattice favor the Si atoms intercalation, thus forming two-dimensional, flat and disordered islands below the Gr layer. Ab-initio molecular dynamics calculations confirm that Gr defects are necessary for Si intercalation at room temperature and show that: i) a hypothetical intercalated silicene layer cannot be stable for more than 8 ps and ii) the corresponding Si atoms completely lose their in-plane order resulting in a random planar distribution and form strong covalent bonds with Ni atoms.

Tumor genomic profiling (TGP) often incidentally identifies germline pathogenic variants (PVs) associated with cancer predisposition syndromes. Methods used by somatic testing laboratories, including germline analysis, differ from designated germline laboratories that have optimized the identification of germline PVs. This study evaluated discrepancies between somatic and germline testing results, and their impact on patients.Chart reviews were carried out at a single institution for patients who had both somatic and designated germline genetic testing. Cases with discrepant results in which germline PVs were not detected by the somatic laboratory or in which variant classification differed are summarized.TGP was carried out on 2811 cancer patients, 600 of whom also underwent designated germline genetic testing. Germline PVs were identified for 109 individuals. Discrepancies between germline genetic testing and tumor profiling reports were identified in 20 cases, including 14 PVs identified by designated germline genetic testing laboratories that were not reported by somatic testing laboratories and six variants with discrepant classifications between the designated germline and somatic testing laboratories. Three PVs identified by designated germline laboratories are targets for poly adenosine diphosphate-ribose polymerase (PARP) inhibitors and resulted in different treatment options. Of the PVs identified by designated germline laboratories, 60% (n = 12) were in genes with established associations to the patients' cancer, and 40% of the PVs were incidental. The majority (90%) of all discrepant findings, both contributory and incidental, changed management recommendations for these patients, highlighting the importance of comprehensive germline assessment.Methods used by somatic laboratories, regardless of the inclusion of germline analysis, differ from those of designated germline laboratories for identifying germline PVs. Unrecognized germline PVs may harm patients by missing hereditary syndromes and targeted therapy opportunities (e.g. anti-programmed cell death protein 1 immunotherapy, PARP inhibitors). Clinicians should refer patients who meet the criteria for genetic evaluation regardless of somatic testing outcomes.

We report a study of the interface between antimony and the prototypical topological insulator Bi

In this study, the CO2 adsorption properties of different metal mixed oxides (MMO) obtained by calcination of different layered double hydroxides (LDH) are addressed. Four types of LDH, with composition $$\left[{{\text{M}}_ {1 - {\text{x}}}^{2 +} {\text{M}}_{\text{x}}^{3 +} \left({\text{OH}} \right)_{2}} \right]^{{\text{x} +}} \cdot[{\text{A}}_{\text{x/n}}^{{\text{n} -}} \cdot {m}{\text{H}}_{2} {\text{O}}]^{{\text{x} -}},$$ where M2+=Zn, Cu, Ni, M3+=Al, x = 0.33, n = 2 and A = CO 3 2− , were studied by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and thermogravimetric analysis coupled with mass spectrometry (TG-MS). Different thermal behaviors upon heating were observed depending on the LDH composition, resulting in the exploitation of different calcination temperatures to convert LDH into mixed metal oxides (MMO). MMO were exposed to ambient air or pure carbon dioxide atmosphere to evaluate CO2 adsorption properties. Aging in ambient condition leads to adsorption of both CO2 and water, from ambient moisture, with variable ratios depending on the MMO composition. Furthermore, all the MMO were demonstrated to be able to adsorb CO2 in pure gas stream, in the absence of moisture. In both ambient and pure CO2 conditions, the performance of MMO is strongly dependent on the metal composition of MMO. In particular, the presence of Cu in the structure turned out to be beneficial in terms of adsorption capacity, with a maximum mass gain for CuAl MMO of 4 and 15% in pure CO2 and in atmospheric conditions, respectively.

Introduction/Background Late onset Pompe disease (LOPD) is an autosomal recessive neuromuscular disorder. Among the other symptoms patients are characterized by a reduction of bone mineral density (BMD) and muscle strength. Moreover there seems to be a cognitive involvement, which has not been well described yet. Therefore, the aim of this study was to assess bone, muscle, and cognitive impairments in all the members of a family affected by LOPD. Material and method We included siblings with same genotype (p.R40X/p.N882fs) affected by LOPD. These patients underwent an experimental evaluation protocol in order to evaluate: BMD, using the dual-energy X-ray absorptiometry (DXA); muscle strength, by Hand Grip Strength Test (HGS); level of independence, using the Functional Independence Measure (FIM); cognitive functions, using Trial Making Test A (TMT-A) and B (TMT-B) and the Stroop Color Test. Results Of 10 siblings with a diagnosis of LOPD, 7 (3 males and 4 females, mean aged 53.71 ± 6.05 years) had the same genotype (p.R40X/p.N882fs). Of these 7 patients, 4 (57.14%) had low BMD values (2 osteoporotic and 2 osteopenic) and hypovitaminosis D ( Conclusion In this study we found low BMD values in more than half of the examined cases, a reduction of muscle strength and a mild attentional and executive deficit. These results testify the necessity of a multidimensional assessment to better investigate all the characteristics of these patients.

Post-infectious bronchiolitis obliterans (PBO) is a rare form of chronic obstructive lung disease in children with few data on the pulmonary function outcome and underlying inflammatory process. The aim of this study was to determine the change in lung function over time and to investigate by bronchoalveolar lavage (BAL) the inflammatory characteristics of pulmonary involvement. Eleven Caucasian children with PBO were evaluated to estimate the average rate of change in lung function indices using a mixed model. The differential cytology and lymphocyte subsets of BAL fluid were analyzed. The median follow-up was 10.2 (IQR 3.2-12) years. The estimated forced expiratory volume in 1 sec (FEV1) had a baseline intercept of 57% predicted (62% predicted after bronchodilator) at 10 years of age which fell at a rate of 1.01% per year whereas the estimated forced expiratory flow 25-75 (FEF25-75) had a baseline intercept of 36% predicted (42% predicted after bronchodilator) at 10 years of age which fell at a rate of 1.04% per year. The estimated FEV1/FVC ratio had a baseline intercept of 70% (74% after bronchodilator) at 10 years of age which declined with an average slope of 1.02% per year (-1.10% per year after bronchodilator). Although the baseline and post-bronchodilator level of estimated FVC was abnormal (68% and 69% predicted, respectively) it did not change significantly with time. The median disease duration at BAL evaluation was 3.7 (IQR 0.7-8) years. The percentage differential cell counts were characterized by a significant increase in neutrophils (median 50%, IQR 1-66%), and a slight increase of lymphocytes (median 14%, IQR 7.5-15%). In conclusion, pulmonary function in childhood PBO is characterized by significant airway obstruction which deteriorates over time. The presence of an ongoing inflammatory process could explain the decline in lung function over time.

The ?-Sn/Ge(111) surface is a prototypical system where the ground state depends on the interplay between lattice and electron dynamics. This surface is characterized by Sn adatoms regularly located on one out of three T4 sites of the bulk terminated Ge(111) surface. We present a pump-probe VUV-IR photoemission study of the temporal dynamics ( 0 - 20 ps) of the Sn 4d core level spectra under optical excitation (IR 800 nm or 2 ?m). The aim is to unveil the complex electron-lattice coupling mechanism involved in the ?-Sn/Ge(111) (?3×?3)R30°3×3 surface phase transition.The photoemission measurements were done at the CELIA facility using the 27th and 29th harmonic of the laser beam produced by the AURORE apparatus. In Fig. 1 a typical photoemission spectrum collected on the ?-Sn/Ge(111) is reported. The Sn 4d core level is characterized by two distinct components as previously reported [2]. These components are assigned to two non-equivalent Sn adatoms where empty and filled surface electronic states are mainly located. The intensity of the Sn 4d components shows different time evolution when the sample is excited by 2 ?m or 800 nm radiation, pointing to different excitation mechanism for the two wavelengths. [1] J. M. Carpinelli, et al. Phys. Rev. Lett. 1997, 79, 2859 [2] J. Avila, et al. Phys Rev. Lett. 1999, 82, 442; R. I. G. Uhrberg, et al. Phys. Rev. Lett. 2000, 85, 1036; Le Lay et al. Appl. Surf. Sci. 1998, 123

The thermal oxidation of the β-Si3N4(0 0 0 1)-8 × 8 surface has been carried out. The spectroscopic characterization has been performed by high resolution core-level and by angle-resolved photoemission spectroscopy. Our findings demonstrate that the surface shows a low but clear reactivity with oxygen. The known resonance ascribed to the 8 × 8 reconstruction results strongly affected by the oxygen dosing, demonstrating the involvement of the topmost nitride atoms.

A decade after the publication of the first paper on nanoribbons (NRs) formed at the Si/Ag(110) surface, the nature of these structures is still under debate. Several studies have proposed that these structures are made up of silicene, a single layer of a buckled honeycomb structure of Si atoms. We report on novel NRs models based on new Si coverage measurements and evaluated using density functional theory simulations. Our models are thermodynamically stable, consistent with the experimental Si and Ag coverages, and yield simulated STM images in excellent agreement with the measured data; in contrast, silicene-based models yield unsatisfactory results.

Silicene was claimed to be a novel silicon allotrope analog of graphene. Based on the evidence that silicon and silver are bulk immiscible, the Ag(111) turned out to be the substrate of election for silicene synthesis. All theoretical models of silicene on Ag(111) rely on this assumption, in contrast with recent findings showing that the silicon grows inside the first layer of the Ag(111) substrate rather than on top of it. Here we report on a combined theoretical and experimental study, unveiling the basic intermixing mechanism between Si and the topmost layer Ag atoms occurring in the nucleation process.

We report the discovery of a nearly-free electronlike resonant state for a ?-Si3N4(0001)-8×8 layer grown on Si(111), as observed by angle-resolved photoemission and scanning tunneling spectroscopy. Comparison with measurements performed on a Si(111)-7×7 surface helped us in the identification of the band. It is found that this parabolic state is degenerate with surface projected bulk bands of the Si(111) substrate.

Synchrotron-based c tended X-ray absorption fine structure spectroscopy (EXAFS). X-ray diffraction at room and high temperature, thermal analyses combined with mass spectrometry of evolved a-as. and chemical analyses contributed to assess the influence of mercury on montmorillonite and vermiculite layers. The adsorbed Hg amount was higher for montmorillonite (Hg=37.7 meq/100 2) than for vermiculite (He-28.0 meq/100 g). The basal spacing for the Hg treated samples was 15.2 (montmorillonite) and 14.5 Angstrom (vermiculite). Thermal and evolved gas spectrometry analyses suggest that Hg was released at T congruent to 230 degreesC and at 600 degreesC for montmorillonite. but at 550. 800 and 860 C for vermiculite. The effect of temperature on Hg release is also apparent when the basal spacing at 230 degreesC for montmorillonite (d(001)=10.3 Angstrom) is compared to that for vermiculite (d(001)=11.8 Angstrom). EXAFS analyses provide qualitative evidence that oxygen atoms occupy the first coordination shell of Hg in both clay minerals. The best fit between observed and calculated spectra is obtained when montroydite is assumed as a reference model compound.

The local structure around the Ce substitutional defects has been investigated by Ce and Nd K-edge EXAFS on Nd2-x Ce x CuO $_{4\pm \delta}$ samples with different dopant concentrations (x = 0.05, 0.10, 0.15 and 0.20) and oxygen amounts. The lattice distortion around the Ce $_{\rm Nd}^\bullet$ can be described as a shrinkage of the oxygen cuboid along the z crystallographic direction. Moreover, the CuO4 planes become corrugated. The lattice distortion is well localized and is largely independent of temperature and Ce and oxygen content. EXAFS measurements made at the Nd-K edge indicate that the local chemical environment of Nd is not distorted. The difference electron density maps, obtained from low temperature single crystal X-ray diffraction data, revealed three strong positive residuals which have been ascribed to cerium (at 0, 0, $z\cong 0.41$ ) and to two non equivalent oxygen apical positions O3 (at 0, 0, $z\cong 0.19$ ) and O4 (at 0, 0 $z\cong 0.24$ ). The electron population of O4 site, which is closer to cerium ( $d_{\rm Ce-O4} = 1.96$ A), is 3-4 times the O3 one.

The thermal oxidation of Ge or As implanted Si single crystals has been investigated for two different oxidation processes (in wet ambient at 920 °C and dry ambient at 1100 °C). Using the atomic force microscopy the oxide morphology and roughness has been determined as a function of the different oxidation processes. The X-ray absorption spectroscopy has been employed to determine the structural coordination around the dopant atoms. We found that the surface roughness is related to the segregation of Ge or As at the oxide/substrate interface, occurring when the oxidation rate is faster than the dopant diffusion, in particular at the higher implanted dose processed in wet ambient. The segregation of Ge at the interface gives rise to the formation of germanium rich alloy region, whereas the segregation of As induces the precipitation of SiAs monoclinic islands. The formation of islands is directly related to the dopant segregation, but their size is not. In fact, after a critical concentration of dopant at the interface is reached, a dissolution of the precipitates takes place. A memory effect causes the continuous growing of the islands, even once the diffusion of Ge or As takes place.

This work reports on the change in the silver–silver interatomic distance dAg–Ag as a function of the coordination number for silver clusters supported on MgO(1 0 0) surfaces. Interatomic distances were determined by means of X-ray absorption spectroscopy (XAS) at the silver K-edge. For coordination number lower than 7 (below an average thickness equivalent to 1 ML), dAg–Ag is contracted with respect to the bulk parameter and scales with cluster size. For coordination numbers ranging between 7 and 10 (between 1 and 3 ML), dAg–Ag increases above the bulk value and shows a tendency to match the MgO(1 0 0) substrate. It then relaxes back to the bulk distance. Coordination numbers found herein successfully compare those derived from a model based on grazing incidence small angle X-ray scattering measurements. At low coverage, the XAS data measured by the total electron yield method exhibits diffraction peaks which are consistent with the presence of structurally coherent islands on the MgO substrate.

The adsorption of CO at 77 K on zirconia-supported tungsten oxide (ZW) samples prepared by equilibrium adsorption or by impregnation and with tungsten content up to 12.4 W atoms nm−2 was studied with the aim of determining the coverage of ZrO2 surface by the supported tungsten oxospecies. As an essential background for quantitative volumetric measurements, ZW samples were investigated by FT-IR spectroscopy to identify the surface sites responsible for the CO adsorption. FT-IR showed that CO adsorbed selectively and irreversibly on Zrcus4+ centers of the support surface, but not on Wcus6+ sites. By volumetric determinations, the coverage of the zirconia surface by tungsten oxospecies was about 50% at maximum, irrespective of the preparation procedure and of the support crystallographic modification (monoclinic or tetragonal). Zirconia coverage remained significantly unchanged after leaching with a NH3 solution that removed tungsten oxospecies not directly interacting with the zirconia surface. This finding indicates that ZrO2 support coverage depends mainly on the tungsten species strongly anchored to the zirconia surface.

The structure of Cu thin layers deposited on the MgO(0 0 1) surface obtained by cleavage in ultra high vacuum has been investigated by in situ X-ray absorption measurements as a function of the metal coverage. By exploiting the polarized nature of the synchrotron radiation it has been possible to measure the Cu–Cu bond length parallel to the substrate surface for coverages in the monolayer range. Extended X-ray absorption fine structure measurements have evidenced a Cu–Cu distance close to that of the bulk metal, resulting from a weak film–substrate interaction irrespective of the copper thickness. Copper oxidation on the MgO surface has not been evidenced. Our results give a direct confirmation that Cu grows in form of clusters and that the film–substrate interaction is weak as previously reported.

EXAFS (Extended X-ray Absorption Fine Structure) and XANES (X-Ray Absorption Near Edge Structure) spectroscopies have been used to probe the local bonding of the artificially layered superconducting (BaCuO2)2/(CaCuO2)n (n = 2, 3, 4) superlattices. Fluorescence-yield measurements have been performed above the Cu and Ba K-edges. This study shows that the charge reservoir (CR) block of the Ba/Ca superlattice contains oxygen vacancies randomly distributed in the CuO2 planes and that the two apical oxygen atoms are displaced out of the Ba plane giving rise to buckled BaO planes. These oxygen atoms have a distorted pyramidal and octahedral coordination around Cu at Ba/Ca interface and in the (BaCuO2) block, respectively.

Polarised extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) spectroscopies have been used to probe the local bonding of the infinite layer compounds CaCuO2 and SrCuO2 and of artificially layered superconducting (BaCuO2)2/(CaCuO2)n and nonsuperconducting (BaCuO2)2/(SrCuO2)2 superlattices. Fluorescence-yield measurements have been performed at T=77 K above the Cu and Ba K-edges. The XANES spectrum of CaCuO2 is described in terms of mixing of electronic configurations in the final state. EXAFS results show that the charge reservoir (CR) block of the Ba/Ca superlattice contains 0.6 oxygen vacancies per unit cell randomly distributed in the CuO2 plane sandwiched between the BaO planes and that the two apical oxygens are not in the Ba plane but are shifted toward Cu by 0.21 A. These oxygens have a pyramidal and distorted octahedral coordination with Cu at the Ba/Ca interface and in the (BaCuO2)2 block, respectively. The results clarify the origin of the oxygen doping mechanism in these artificially layered compounds.

Interfaces between ferromagnetic (FM) and antiferromagnetic (AFM) materials constitute one of the active elements of new magneto-electronic devices, which exploit the electron spin rather than its charge for information processing and transfer. The exchange interactions at the interface formed between the FM and the AFM layers result in an unidirectional magnetic anisotropy, the so called exchange bias, of which a quantitative explanation is presently lacking [ ]. Exchange bias leads to a shift of the magnetic hysterisis curve. In many cases, real FM/AFM interfaces are not ideal in their structure and chemistry and their atomic configuration is expected to have a very strong influence on the magnetic couplings between the two materials. We investigated the case of an epitaxial system, Fe/NiO(001), taken as a model for a FM metal / AFM oxide interface, and obtained a combined experimental and theoretical description for it, which provides new insight in the understanding of magnetic couplings in such systems. The sample used for this study was a UHV grown 2 ML Fe/10 ML NiO/Ag(001) multilayer, capped by a 10 nm thick Au layer to prevent the sample contamination by the atmosphere. Fe K-edge x-ray absorption fine structure (XAFS) measurements were performed at the BM08 “GILDA” beamline. We exploited the polarization dependence of the XAFS cross section in order to separately probe the in-plane and out-of-plane structure [ ]. The background subtracted XAFS spectra in the two geometries are shown in Figure1a. Figure 1b shows the corresponding magnitude of the Fourier transforms and the results of structural fits. The fitting of the extended range spectra was performed assuming the formation of a planar FeO-like layer at the Fe/NiO interface (see model in Figure 2). The FeO-like layer exhibits a buckling, with O and Fe atoms respectively shifted towards and away from the underlying NiO substrate. Moreover, the distance between the last NiO plane and the average position of the FeO plane is 7 % larger than the interplanar distance of bulk NiO. A body-centered-tetragonal (bct) Fe-Ni phase is present on top of the interfacial FeO layer. We have compared the structural parameters obtained by the XAFS analysis to the results of density functional theory calculations performed by means of the all-electron linearized augmented plane wave method + local orbital in the generalized gradient approximation. The atomic configurations of the structurally relaxed system compare very well with the experimental ones. In particular, the numerical agreement between the values for the buckling of the FeO layer (experiment: 0.29 ± 0.07 Å; theory: 0.34 Å) and for the expanded distance between the FeO layer and the underlying NiO (exp. 2.24 ± 0.08 Å; th. 2.25 Å) is notable. Our calculations also allowed to evaluate the spin magnetic moment of the Fe atoms at the interface, providing original insight into the relation between structure and magnetic properties. We compared the values obtained assuming the presence of a pure, pseudomorphic, Fe layer and the formation of an oxidized FeO layer. A significant increase of approximately 0.6 μB (from 2.6 μB to 3.2 μB) in the presence of the distorted FeO layer was found. The origin of this change lies in a depopulation of minority spin d orbitals involved in the Fe-O bonds. The Fe atoms of the interfacial FeO layer assumed in our model are in fact more coordinated with oxygen atoms than Fe atoms situated in the first layer of the ideal Fe/NiO interface, therefore a higher spin polarization is achieved. Uncompensated moments coming from the interfacial FeO layer, which may couple ferromagnetically with the Fe layer, are expected to influence dramatically the exchange interaction at the Fe/NiO interface, with significant consequences also on the exchange bias mechanism. In summary, we give evidence for the presence of a structurally distorted FeO layer at the Fe/NiO(001) interface, in which...

Six volleyball players developed weakness and atrophy of the infraspinatus muscle on the dominant side. Electromyography (EMG) disclosed denervation and motor unit loss restricted to the infraspinatus muscle, the supraspinatus and other shoulder muscles remaining normal. Infraspinatus neuropathy may occur as a professional hazard in volleyball players. A lesion of the suprascapular nerve at the spinoglenoid notch is implied.

A simple cell, assembled with commercial parts, suitable for in situ X-ray-absorption spectroscopy measurements of heterogeneous catalysts, has been designed. The cell, light and easy to handle, allows thermal treatments of the sample under investigation up to 823 K in a reducing or oxidizing atmosphere and measurements at both high and liquid-nitrogen temperature. The cell was tested by studying the decomposition, in an oxygen flow, of ammonium metatungstate to WO3. Extended X-ray absorption fine-structure measurements of the ammonium metatungstate before and after a thermal treatment at 773 K are reported.

Polarized X-ray absorption fine structure (XAFS) measurements at the Co K and Pt L3 edges show that the perpendicular magnetic anisotropy found in epitaxial fcc CoPt3 (111) films stems from the existence of anisotropic local ordering. Such ordering, induced during the codeposition process and dependent on the growth temperature, is characterized by preferential CoCo pairs in the film plane, balanced by preferential CoPt pairs out of the plane, resulting from some Co 2D-segregation. Polarized XAFS at the Pt edge reveals similar anisotropic local ordering in epitaxial hcp Co3Pt (0001) films exhibiting a larger magnetocrystalline anisotropy compared to that of bulk hcp Co. Besides, a polarization dependence of the Co XANES profile is observed only for the Co3Pt films exhibiting hcp symmetry.

In order to provide a structural basis for a physical understanding of exchange bias in metal/magnetic-oxide interfaces, we have determined the structure of the Fe/NiO(001) interface by means of x-ray absorption spectroscopy and ab initio density functional theory calculations. A Fe-Ni alloyed phase on top of an interfacial FeO planar layer is formed. The FeO layer exhibits a 7% expanded interlayer distance and a 0.3 angstrom buckling; its presence is predicted to increase the spin magnetic moment of the interface Fe atoms by 0.6 mu(B), compared to the ideally abrupt interface.

Establishment of infection and disease implies modifications in the genetic programmes of the cell systems that are involved and the differential expression of genes in both parasite and host. In order to identify and isolate relevant genes of the fungus, Histoplasma capsulatum , in which expression is specifically induced during its interaction with murine macrophages (Mф), we performed a comparative analysis of the pattern of gene expression of the fungus before and after exposure to, and internalization into Mф by using differential display reverse transcriptase-PCR (DDRT-PCR). Using a limited set of primer combinations, six cDNA fragments of H. capsulatum were identified and isolated; five representing fungal genes in which expressions were enhanced during Mф infection, whereas one mRNA fragment was down-regulated. Slot blots followed by Northern blot analyses confirmed that the transcripts detected with cDNA clones were over expressed after 1 h of Mф infection, whereas no transcripts were detected with mRNA purified from H. capsulatum before infection. Sequence analyses and database searches revealed no significant homology to any known sequence for five of these clones. One of the clones showed homology to the rat p105 kD protein, and to the p100 kD co-activator proteins of human and Caenorhabditis elegans . To our knowledge, this is the first experimental evidence that specific genes are differentially expressed by a fungal pathogen when it is exposed to, and phagocytosed by Mф. Furthermore, these results show that the DDRT-PCR procedure has adequate sensitivity to detect fungal genes induced during parasite–host interaction to identify potential new targets that can be used to develop new antifungal drugs.

Two-dimensional systems, such as ultrathin epitaxial films and superlattices, exhibit magnetic properties distinct from bulk materials. Despite the extensive research on the magnetic properties of metal nano-structures and more recently metal oxide interfaces containing magnetic ions, the investigation of magnetic semiconductors with reduced dimensions is still moving its first steps. The interest in this field is boosted by the hoped development of spintronics devices. In this respect Mn based alloys are promising elements for spin injection in semiconductors given the half full shell and therefore large atomic spin of Mn atoms. As the efficiency in the spin injection depends on the interface quality, surface alloys of semiconductors containing Mn atoms can be used to model the interface magnetic and electronic properties. In particular, a careful study of Mn coordination, spin state, charge and magnetic ordering as a function of Mn content and/or preparation method can be extremely important for the development of spintronic-based devices. In spite of this strong interest only few papers deal with the first stages of the Mn/GaAs(001) interface both on the (2×4) and c(4×4) reconstructed GaAs(001) surfaces. Here we present an investigation, by means of X-ray Absorption Spectroscopy (XAS) and X-ray Magnetic Circular Dichroism (XMCD) at the Mn L2,3 absorption edges, of the magnetic properties and the local atomic coordination of a two-dimensional system obtained by Mn atoms ordering on the GaAs(001) surface for Mn thickness ranging from 1/8 to 1 ML. The proposed system, already extensively investigated by STM and LEED by our group, showed a strong dependence of the Mn/GaAs(001) surface reconstruction on the preparation method. Further, the surface reconstruction undergoes a phase transition from (2×1) to (2×2) when increasing the Mn coverage on a hot substrate (390°C) up to 1/2 monolayer (ML). [1] The combination of XAS and XMCD investigation has allowed obtaining information on the local atomic coordination around the Mn sites and its influence on the surface magnetic properties. In order to study the magnetic anisotropy of the atomic rows at the surface, XMCD and XAS measurements have been performed for different orientations of the magnetic field B with respect to the sample surface. [1] S. Colonna et al. J. App. Phys. 109 (2011) 123522

The quest for silicon-based materials with atoms arranged in a 2D honeycomb structure like graphene, i.e. silicene, has revived the interest for the Si/Ag(110) system which forms remarkable linear nanostructures, coined, "silicon nanoribbons". We present a systematic investigation by Scanning Tunneling Microscopy and Low Energy Electron Diffraction of the Si/Ag(110) system as a function of deposited silicon amount and deposition temperature. Such systematic investigation reveals a complex interplay between the deposited Si amount and deposition temperature, resulting in a rich existence diagram of self-assembled nanostructures and surface reconstructions. Several novel findings are discussed in this work which call for a revisitation of the theoretical structural models and clarify contradicting results reported in literature. In particular, the deposition temperature is demonstrated to be a key parameter to control the width of the produced Si nanoribbons: 0.8 nm-wide nanoribbons are obtained for deposition temperatures lower than 460 K, whereas for temperature higher than 460 K the majority of nanoribbons is 1.6 nm-wide. Interestingly, the massive linear nanostructures recently reported to be "multilayer silicene" nanoribbons, and supposed to form as the deposited silicon amount exceeds full coverage, are also observed at low silicon coverage as the deposition temperature is increased above 460 K. On the other hand, for Si amount higher than one monolayer the surface presents a certain degree of disorder with patches of c(8×4) reconstruction, that are demonstrated to be responsible for the ×4 periodicity detected by LEED measurements and not adequately interpreted in previous papers. Finally, the large collection of Scanning Tunnelling Microscopy images acquired for the systematic study as a function of the different preparation parameters allowed also, based on a sound statistical analysis, to single out image artifacts that may explain contradicting results appeared in previous papers.

A high-resolution electron energy loss investigation of the Ag- and Au-GaAs(110) interfaces is presented. The loss spectra (0.5≤E loss ≤5 e V) show clearly a broad feature centred at 1.2 eV, that is within the energy gap, due to the metal coverage. This structure, which starts appearing at coverages as low as 0.1 A, becomes undetectable at coverages of 24 A of Ag and 1.6 A of Au. The gap energy region has been examined on several freshly cleaved surfaces. In the case of bad cleaveges, a peak similar to that induced by the metal overlayer develops, a fact which supports mechanisms ascribing the Fermi level pinning to defect states.